/*
Copyright 2023 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package endpoints

// Copy from https://github.com/aws/aws-sdk-go
// May have been modified by Beijing Volcanoengine Technology Ltd.

import (
	"fmt"
	"regexp"

	"k8s.io/autoscaler/cluster-autoscaler/cloudprovider/volcengine/volcengine-go-sdk/volcengine/volcengineerr"
)

// Options provide the configuration needed to direct how the
// endpoints will be resolved.
type Options struct {
	// DisableSSL forces the endpoint to be resolved as HTTP.
	// instead of HTTPS if the service supports it.
	DisableSSL bool

	// Sets the resolver to resolve the endpoint as a dualstack endpoint
	// for the service. If dualstack support for a service is not known and
	// StrictMatching is not enabled a dualstack endpoint for the service will
	// be returned. This endpoint may not be valid. If StrictMatching is
	// enabled only services that are known to support dualstack will return
	// dualstack endpoints.
	UseDualStack bool

	// Enables strict matching of services and regions resolved endpoints.
	// If the partition doesn't enumerate the exact service and region an
	// error will be returned. This option will prevent returning endpoints
	// that look valid, but may not resolve to any real endpoint.
	StrictMatching bool

	// Enables resolving a service endpoint based on the region provided if the
	// service does not exist. The service endpoint ID will be used as the service
	// domain name prefix. By default the endpoint resolver requires the service
	// to be known when resolving endpoints.
	//
	// If resolving an endpoint on the partition list the provided region will
	// be used to determine which partition's domain name pattern to the service
	// endpoint ID with. If both the service and region are unknown and resolving
	// the endpoint on partition list an UnknownEndpointError error will be returned.
	//
	// If resolving and endpoint on a partition specific resolver that partition's
	// domain name pattern will be used with the service endpoint ID. If both
	// region and service do not exist when resolving an endpoint on a specific
	// partition the partition's domain pattern will be used to combine the
	// endpoint and region together.
	//
	// This option is ignored if StrictMatching is enabled.
	ResolveUnknownService bool
}

// Set combines all of the option functions together.
func (o *Options) Set(optFns ...func(*Options)) {
	for _, fn := range optFns {
		fn(o)
	}
}

// DisableSSLOption sets the DisableSSL options. Can be used as a functional
// option when resolving endpoints.
func DisableSSLOption(o *Options) {
	o.DisableSSL = true
}

// UseDualStackOption sets the UseDualStack option. Can be used as a functional
// option when resolving endpoints.
func UseDualStackOption(o *Options) {
	o.UseDualStack = true
}

// StrictMatchingOption sets the StrictMatching option. Can be used as a functional
// option when resolving endpoints.
func StrictMatchingOption(o *Options) {
	o.StrictMatching = true
}

// ResolveUnknownServiceOption sets the ResolveUnknownService option. Can be used
// as a functional option when resolving endpoints.
func ResolveUnknownServiceOption(o *Options) {
	o.ResolveUnknownService = true
}

// A Resolver provides the interface for functionality to resolve endpoints.
// The build in Partition and DefaultResolver return value satisfy this interface.
type Resolver interface {
	EndpointFor(service, region string, opts ...func(*Options)) (ResolvedEndpoint, error)
}

// ResolverFunc is a helper utility that wraps a function so it satisfies the
// Resolver interface. This is useful when you want to add additional endpoint
// resolving logic, or stub out specific endpoints with custom values.
type ResolverFunc func(service, region string, opts ...func(*Options)) (ResolvedEndpoint, error)

// EndpointFor wraps the ResolverFunc function to satisfy the Resolver interface.
func (fn ResolverFunc) EndpointFor(service, region string, opts ...func(*Options)) (ResolvedEndpoint, error) {
	return fn(service, region, opts...)
}

var schemeRE = regexp.MustCompile("^([^:]+)://")

// AddScheme adds the HTTP or HTTPS schemes to a endpoint URL if there is no
// scheme. If disableSSL is true HTTP will set HTTP instead of the default HTTPS.
//
// If disableSSL is set, it will only set the URL's scheme if the URL does not
// contain a scheme.
func AddScheme(endpoint string, disableSSL bool) string {
	if !schemeRE.MatchString(endpoint) {
		scheme := "https"
		if disableSSL {
			scheme = "http"
		}
		endpoint = fmt.Sprintf("%s://%s", scheme, endpoint)
	}

	return endpoint
}

// EnumPartitions a provides a way to retrieve the underlying partitions that
// make up the SDK's default Resolver, or any resolver decoded from a model
// file.
//
// Use this interface with DefaultResolver and DecodeModels to get the list of
// Partitions.
type EnumPartitions interface {
	Partitions() []Partition
}

// A Partition provides the ability to enumerate the partition's regions
// and services.
type Partition struct {
	id, dnsSuffix string
	p             *partition
}

// DNSSuffix returns the base domain name of the partition.
func (p Partition) DNSSuffix() string { return p.dnsSuffix }

// ID returns the identifier of the partition.
func (p Partition) ID() string { return p.id }

// EndpointFor attempts to resolve the endpoint based on service and region.
// See Options for information on configuring how the endpoint is resolved.
//
// If the service cannot be found in the metadata the UnknownServiceError
// error will be returned. This validation will occur regardless if
// StrictMatching is enabled. To enable resolving unknown services set the
// "ResolveUnknownService" option to true. When StrictMatching is disabled
// this option allows the partition resolver to resolve a endpoint based on
// the service endpoint ID provided.
//
// When resolving endpoints you can choose to enable StrictMatching. This will
// require the provided service and region to be known by the partition.
// If the endpoint cannot be strictly resolved an error will be returned. This
// mode is useful to ensure the endpoint resolved is valid. Without
// StrictMatching enabled the endpoint returned my look valid but may not work.
// StrictMatching requires the SDK to be updated if you want to take advantage
// of new regions and services expansions.
//
// Errors that can be returned.
//   - UnknownServiceError
//   - UnknownEndpointError
func (p Partition) EndpointFor(service, region string, opts ...func(*Options)) (ResolvedEndpoint, error) {
	return p.p.EndpointFor(service, region, opts...)
}

// Regions returns a map of Regions indexed by their ID. This is useful for
// enumerating over the regions in a partition.
func (p Partition) Regions() map[string]Region {
	rs := map[string]Region{}
	for id, r := range p.p.Regions {
		rs[id] = Region{
			id:   id,
			desc: r.Description,
			p:    p.p,
		}
	}

	return rs
}

// Services returns a map of Service indexed by their ID. This is useful for
// enumerating over the services in a partition.
func (p Partition) Services() map[string]Service {
	ss := map[string]Service{}
	for id := range p.p.Services {
		ss[id] = Service{
			id: id,
			p:  p.p,
		}
	}

	return ss
}

// A Region provides information about a region, and ability to resolve an
// endpoint from the context of a region, given a service.
type Region struct {
	id, desc string
	p        *partition
}

// ID returns the region's identifier.
func (r Region) ID() string { return r.id }

// Description returns the region's description. The region description
// is free text, it can be empty, and it may change between SDK releases.
func (r Region) Description() string { return r.desc }

// ResolveEndpoint resolves an endpoint from the context of the region given
// a service. See Partition.EndpointFor for usage and errors that can be returned.
func (r Region) ResolveEndpoint(service string, opts ...func(*Options)) (ResolvedEndpoint, error) {
	return r.p.EndpointFor(service, r.id, opts...)
}

// Services returns a list of all services that are known to be in this region.
func (r Region) Services() map[string]Service {
	ss := map[string]Service{}
	for id, s := range r.p.Services {
		if _, ok := s.Endpoints[r.id]; ok {
			ss[id] = Service{
				id: id,
				p:  r.p,
			}
		}
	}

	return ss
}

// A Service provides information about a service, and ability to resolve an
// endpoint from the context of a service, given a region.
type Service struct {
	id string
	p  *partition
}

// ID returns the identifier for the service.
func (s Service) ID() string { return s.id }

// ResolveEndpoint resolves an endpoint from the context of a service given
// a region. See Partition.EndpointFor for usage and errors that can be returned.
func (s Service) ResolveEndpoint(region string, opts ...func(*Options)) (ResolvedEndpoint, error) {
	return s.p.EndpointFor(s.id, region, opts...)
}

// Regions returns a map of Regions that the service is present in.
//
// A region is the Volcengine region the service exists in. Whereas a Endpoint is
// an URL that can be resolved to a instance of a service.
func (s Service) Regions() map[string]Region {
	rs := map[string]Region{}
	for id := range s.p.Services[s.id].Endpoints {
		if r, ok := s.p.Regions[id]; ok {
			rs[id] = Region{
				id:   id,
				desc: r.Description,
				p:    s.p,
			}
		}
	}

	return rs
}

// Endpoints returns a map of Endpoints indexed by their ID for all known
// endpoints for a service.
//
// A region is the Volcengine region the service exists in. Whereas a Endpoint is
// an URL that can be resolved to a instance of a service.
func (s Service) Endpoints() map[string]Endpoint {
	es := map[string]Endpoint{}
	for id := range s.p.Services[s.id].Endpoints {
		es[id] = Endpoint{
			id:        id,
			serviceID: s.id,
			p:         s.p,
		}
	}

	return es
}

// A Endpoint provides information about endpoints, and provides the ability
// to resolve that endpoint for the service, and the region the endpoint
// represents.
type Endpoint struct {
	id        string
	serviceID string
	p         *partition
}

// ID returns the identifier for an endpoint.
func (e Endpoint) ID() string { return e.id }

// ServiceID returns the identifier the endpoint belongs to.
func (e Endpoint) ServiceID() string { return e.serviceID }

// ResolveEndpoint resolves an endpoint from the context of a service and
// region the endpoint represents. See Partition.EndpointFor for usage and
// errors that can be returned.
func (e Endpoint) ResolveEndpoint(opts ...func(*Options)) (ResolvedEndpoint, error) {
	return e.p.EndpointFor(e.serviceID, e.id, opts...)
}

// A ResolvedEndpoint is an endpoint that has been resolved based on a partition
// service, and region.
type ResolvedEndpoint struct {
	// The endpoint URL
	URL string

	// The region that should be used for signing requests.
	SigningRegion string

	// The service name that should be used for signing requests.
	SigningName string

	// States that the signing name for this endpoint was derived from metadata
	// passed in, but was not explicitly modeled.
	SigningNameDerived bool

	// The signing method that should be used for signing requests.
	SigningMethod string
}

// So that the Error interface type can be included as an anonymous field
// in the requestError struct and not conflict with the error.Error() method.
type volcengineerror volcengineerr.Error

// A EndpointNotFoundError is returned when in StrictMatching mode, and the
// endpoint for the service and region cannot be found in any of the partitions.
type EndpointNotFoundError struct {
	volcengineerror
	Partition string
	Service   string
	Region    string
}

// A UnknownServiceError is returned when the service does not resolve to an
// endpoint. Includes a list of all known services for the partition. Returned
// when a partition does not support the service.
type UnknownServiceError struct {
	volcengineerror
	Partition string
	Service   string
	Known     []string
}

// NewUnknownServiceError builds and returns UnknownServiceError.
func NewUnknownServiceError(p, s string, known []string) UnknownServiceError {
	return UnknownServiceError{
		volcengineerror: volcengineerr.New("UnknownServiceError",
			"could not resolve endpoint for unknown service", nil),
		Partition: p,
		Service:   s,
		Known:     known,
	}
}

// String returns the string representation of the error.
func (e UnknownServiceError) Error() string {
	extra := fmt.Sprintf("partition: %q, service: %q",
		e.Partition, e.Service)
	if len(e.Known) > 0 {
		extra += fmt.Sprintf(", known: %v", e.Known)
	}
	return volcengineerr.SprintError(e.Code(), e.Message(), extra, e.OrigErr())
}

// String returns the string representation of the error.
func (e UnknownServiceError) String() string {
	return e.Error()
}

// A UnknownEndpointError is returned when in StrictMatching mode and the
// service is valid, but the region does not resolve to an endpoint. Includes
// a list of all known endpoints for the service.
type UnknownEndpointError struct {
	volcengineerror
	Partition string
	Service   string
	Region    string
	Known     []string
}

// NewUnknownEndpointError builds and returns UnknownEndpointError.
func NewUnknownEndpointError(p, s, r string, known []string) UnknownEndpointError {
	return UnknownEndpointError{
		volcengineerror: volcengineerr.New("UnknownEndpointError",
			"could not resolve endpoint", nil),
		Partition: p,
		Service:   s,
		Region:    r,
		Known:     known,
	}
}

// String returns the string representation of the error.
func (e UnknownEndpointError) Error() string {
	extra := fmt.Sprintf("partition: %q, service: %q, region: %q",
		e.Partition, e.Service, e.Region)
	if len(e.Known) > 0 {
		extra += fmt.Sprintf(", known: %v", e.Known)
	}
	return volcengineerr.SprintError(e.Code(), e.Message(), extra, e.OrigErr())
}

// String returns the string representation of the error.
func (e UnknownEndpointError) String() string {
	return e.Error()
}
